1. Field of the Invention
The present invention relates to a floating magnetic head held in an inline manner in an apparatus having a fixed magnetic disc(s), and, more particularly, to a monolithic type magnetic head revealing improved electromagnetic conversion characteristics and reliability.
2. Description of the Prior art
Hitherto, magnetic discs serving as magnetic a recording media have been mainly manufactured by coating oxide magnetic powder to an aluminum alloy substrate. However, recently, a fixed magnetic disc of a small size which is capable of recording data at high density, with the magnetic layer formed by a plating or a sputtering method, has been widely used.
As a floating magnetic head for use in a small fixed magnetic disc apparatus of the type described above, there has been available a monolithic type floating magnetic head arranged in such a manner that its a slider is made of a magnetic material, such as Mn-Zn ferrite, and the thus made slider constitutes a portion of a main magnetic circuit. As a result, the monolithic type floating magnetic head possesses a high inductance and shows high output voltage at reading. The floating type magnetic head can be held by a standard method in which the backside of a slider is bonded to a holding member, which is provided for a load arm supported in a cantilever manner, in such a manner that the longitudinal central axes of the slider and the holding member are made substantially perpendicular to each other. The floating type magnetic head can be held by an inline method in which the longitudinal axes of the slider and the holding member substantially coincide with each other. In recent years, the inline method has been widely employed in the small magnetic disc apparatus because a space saving advantage can be obtained.
FIG. 6 is a perspective view which illustrates a conventional monolithic type floating magnetic head which is shown in the form of a slider composed of magnetic cores 1 and 2. The magnetic core 1 having air bearing surfaces 3 (hereinafter sometimes called "ABS") and a center rail 4 and the magnetic core 2 having an aperture 12 for coil winding (omitted from illustration) are, by using a bonding glass, integrally connected to each other at the central rail 4 via a magnetic gap 13 holding a gap glass.
The standard method, which is one of the methods of holding the floating magnetic head structured as described above, is arranged in such a manner that the backside of the core 1 is, as shown in FIG. 7a is bonded to the holding member 5 in such a manner that the magnetic head is positioned perpendicularly to the holding member 5. Therefore, a reinforcing adhesive 16 is applied to intersection portions between the core 1 and the holding member 5 in such a manner that it is applied to the side surface of the core 1 and the lower surface (the lower surface when viewed in a state where the magnetic head is used) of the holding member 5. As a result, the bonding strength can be increased. Furthermore, the adhesive does not adhere to the core 2 on which the coil is wound since the gap line is positioned outside the holding member. Consequently, it has not been necessary to implement any special means for preventing the deterioration in the electromagnetic conversion characteristics due to the deformation in a recessed shape taken place in a portion adjacent to the magnetic gap of the center rail.
The floating magnetic head is positioned in soft contact with the magnetic disc by the biased force of a spring when the rotation of the magnetic disc is stopped. However, air on the disc surface is moved when the disc is being rotated, causing force capable of floating the subject side of the slider to be generated. As a result, the floating magnetic head floats by about 0.2 to 0.3 .mu.m. If the magnetic head can be stably floated by a predetermined height, stable electromagnetic conversion characteristics at the time of performing the recording and reading operations can be obtained.
However, the conventional inline method has been arranged in such a manner that only the backside of the core having ABS and the surface of the holding member are connected to each other by an adhesive without special measures for reinforcing the bonding strength (as disclosed in, for example, Japanese Patent Publication JP-A-63-149812). Therefore, satisfactorily high bonding strength cannot be realized in comparison to that obtainable from the standard method. If an excessive quantity of the adhesive is applied for the purpose of increasing the bonding strength, a problem arises in that the adhesive will pass the gap line and the same undesirably adheres to the core 2 on which the coil is formed. If the adhesive adheres to the core on which the coil is wound, the core of the monolithic magnetic head is undesirably pulled toward the holding member. Consequently, a problem arises in that a deformation in a recessed shape takes place in a portion adjacent to the magnetic gap of the center rail, causing the electromagnetic conversion characteristics of the magnetic head to be deteriorated.
FIGS. 8a and 8b illustrate the relationship between the position of the monolithic type floating magnetic head to which the adhesive is applied and the quantity of deformation in a recessed shape (designated by a phantom line) taken place in the portion adjacent to the magnetic gap of the center rail. The magnetic head, that is, the slider comprises the core 1 made of polycrystals of Mn-Zn ferrite and having ABS, the slider being arranged in such a manner that the entire length is 5 mm, the width is 3.5 mm and the height is 1.3 mm. The slider further comprises the core 2 on which a coil is wound. Referring to FIGS. 8a and 8b, numeral 0 (zero) on the axis of abscissa shows the position of the gap line, -0.3 mm shows the position the end line or boundary line of adhesive on the core 2 which is positioned away from the gap line by a distance of 0.3 mm and +0.3 mm shows the position of the same on the core 1 which is positioned away from the gap line by a distance of 0.3 mm. The axis of ordinate stands for the quantity of the deviation of a portion around the magnetic gap of the center rail of the magnetic head. The dark section shows the maximum and the minimum values of the quantity of the deformation. If the adhesive adheres on the core 2 at the portion of 0.3 mm distance from the gap line, the maximum quantity (.DELTA.x .mu.m) of the deformation will become larger than a quantity of 0.01 .mu.m which is estimated to be an allowable limit and which does not influence the electromagnetic conversion characteristics.
In order to overcome the above-described problems experienced with the inline method, a structure has been disclosed in JP-A-63-149812 in which a groove is longitudinally formed along the central axis of a magnetic core having ABS whereby the bonding strength is increased. According to this disclosure, although satisfactorily high bonding strength can be obtained, the adhesion of the adhesive to the core on which the coil is wound cannot be prevented completely. Namely, a flow of the adhesive in the longitudinal direction cannot be prevented. Therefore, the above described problems have not heretofore been overcome.